Coolant Temperature Sensor/Switch (For Computer): Description and Operation

PURPOSE/OPERATION
The engine coolant temperature sensor converts the engine coolant temperature to voltage, and to inputs that voltage (as signals) to the engine control module. The engine control module, based upon those signals, regulates the amount of fuel injection and the fast-idle speed when the engine is cold.
5 Volts is supplied to the engine coolant temperature sensor by the engine control module. It passes through the engine coolant temperature sensor, which is a type of resistor, and is grounded at the engine control module.
The engine coolant temperature sensor terminal voltage varies in accordance with the temperature of the engine coolant, becoming lower when the temperature of the engine coolant increases and higher as the temperature decreases.